Thesis (Ph. D.)--Auburn University. / Abstract. Vita. Includes bibliographical references (p. 73-80).

Inaug.-Diss.--Königsberg.

An investigation of the sodium aluminate-sodium nitrate system was conducted. The effect of sodium nitrate on the solubility of aluminum is important to the retrieval of waste from the tanks at the Hanford nuclear facility located in the state of Washington. Experiments were performed on the NaAlO2 - NaNO3 - H2O system at 25?aC and 50?aC. The results obtained from these experiments were then compared to predictions from the Environmental Simulation Program (ESP, OLI Systems, Inc.) and available literature data. The presence of sodium nitrate increased the solubility of sodium aluminate in water. Sodium nitrate exhibited a greater effect on the solubility of sodium aluminate at higher temperature. Error analysis of the experimental data was performed and indicated that the experimental molalities were accurate to within an average of +3%. The measured data will be used to improve existing databases for ESP.

Nitric oxide (NO) and carbon monoxide (CO) gases, alone or with oxalate, phytate, or ethylenediaminetetraacetate (EDTA) were tested for antibotulinal activity as substitutes for sodium nitrite in ground pork inoculated with spores of Clostridium botulinum, then abused by storage at 277°C. Nitric oxide with 250 ppm oxalate or phytate was most inhibitory, while NO alone was as effective as 156 ppm sodium nitrite for inhibition of gas and botulinal toxin production in the meat system. All swollen samples contained very low levels of residual nitrite, but nitroso heme and soluble iron content did not change compared with unswollen samples of the same treatment while total heme content decreased slightly. Binding iron in the meat system did not appear to be sufficient for botulinal inhibition. Apparently, residual nitrite must be present to react directly with the botulinal cell, inhibiting growth. NO gas would not be a practical subsitute for sodium nitrite in curing, since nitrite itself is formed when meat is blended in the presence of this gas. Neither could CO be used in meat curing, since the pink color of raw, CO-treated meat disappeared after cooking. More importantly, all samples treated with CO swelled rapidly and contained botulinal toxin.

A novel mirror finishing method using a conductive polymer as the tool electrode is presented. It has been known that the conductive polymers have many advantages, such as to conduct a micro-current, to be easily processed into various shapes, to hold abrasives, and to have an excellent wear resistance. The effects of particle size, machining time, concentration of electrolyte, working current, and load on the surface roughness and the removal depth of SUS-304 stainless steel are investigated.When the operative parameters are set for the particle size of 3 £gm, the concentration of electrolyte of 10 wt%, the working current ranged from 10 to 20 mA, and the load of 10 N, the surface roughness Rmax, which originally is 1.4 £gm, can be reduced to 0.17~0.24 £gm after the machining time of 3 min. The surface roughness Ra can be achieved to 7.897 nm under the optimal condition. In addition, experimental results show that there is an optimal region of the working current at the concentration of electrolyte of 10 wt%. According to the surface profiles and SEM micrographs, three machining regions can be classified as (1) the mechanical polishing region, (2) the electro-chemical buffing (ECB) region, and (3) the excessive corrosion region. To achieve a high-quality mirror-like surface, the machining region must be operated at the ECB region.

The present work investigates, numerically, the process of melting and solidification in hollow vertical cylinders, filled with air and phase change material (PCM). The PCM used is sodium nitrate, which expands upon melting. Therefore, a void must be present within the cylinder, which is filled with air. The influence of cylinder shape on melting time is determined. The numerical model takes both conductive and convective heat transfer into account during the melting process. The Volume-of-Fluid (VOF) model is used to track the interface between the PCM and air as the PCM melts. Three dimensionless numbers represent the characteristics of the problem, which are the Grashof, Stefan, and Prandtl numbers. The Stefan and Prandtl numbers are held constant, while the Grashof number varies. Inner Aspect Ratio (AR) is used to characterize the shape of the cylinder, which is defined as the ratio of the height to the diameter of the vertical cylinder. In this study, a range of AR values from 0.23 to 10 is investigated. Cylinders with small AR, corresponding to high Grashof numbers, lead to lower melting times compared with cylinders with high AR. The molten PCM velocity was also influenced greatly by this difference between solid PCM shape between high and low AR cases. Cylinders with small AR, corresponding to high Grashof numbers, lead to higher solidification times compared with cylinders with high AR. It was found that the velocity decreased during the solidification process, but the shape of the cylinder had an effect on the decrease. Natural convection velocity was found to decrease during the solidification process and, therefore, its effects diminish as solidification proceeds.

Orientador: Marise Aparecida Rodrigues Pollonio / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-16T12:31:59Z (GMT). No. of bitstreams: 1 Nascimento_Renatado_M.pdf: 1842864 bytes, checksum: ff48ba117e4d598457a6c594bc8eefaf (MD5) Previous issue date: 2010 / Resumo: No desenvolvimento de produtos cárneos com apelos saudáveis, a redução de sódio e a substituição de nitrito de sódio são relevantes estratégias a serem implementadas pela indústria de processamento. Embora, já seja possível encontrar em alguns mercados produtos cárneos com redução de sódio, a produção desses itens com aceitação sensorial e desempenho tecnológico ainda é um grande desafio. Este trabalho tem o objetivo de avaliar a influência da redução de cloreto de sódio e a substituição do nitrito de sódio por extrato vegetal em embutidos cozidos de peru. Cloreto de potássio foi utilizado para substituir total ou parcialmente cloreto de sódio combinado com um mascarador comercial de sabor amargo nas formulações estudadas. Na pesquisa de substituição de nitrito de sódio em embutido cozido de peito de peru, extrato vegetal de aipo foi aplicado como fonte de nitrato e cultura starter como fonte redutora. Os níveis de substituição de cloreto de sódio por cloreto de potássio avaliados foram: 25%, 50% e 75%. Na primeira etapa do trabalho avaliou-se a redução de cloreto de sódio com foco nos atributos sensoriais. De acordo com testes afetivos de Diferença do Controle e de Aceitação, foi possível concluir que a redução de 25% de NaCl é possível de ser realizada sem afetar a aceitação do produto. Na segunda etapa, avaliou-se o processo de fabricação mais indicado para aplicação do extrato de aipo e cultura starter como substitutos do nitrito de sódio. Finalmente, na terceira etapa foram elaboradas formulações com substituição de NaCl por KCl e mascarador de sabor amargo (25%, 50% e 75% de substituição) com adição de nitrito de sódio e com substituição de nitrito de sódio por extrato de aipo, como fonte de nitrato, e cultura starter, como fonte redutora. Estudou-se a estabilidade dessas formulações ao longo de 60 dias de armazenagem à temperatura de 4°C, através de determinações físico-químicas, instrumentais, sensoriais e microbiológicas. Observou-se que todas as formulações mantiveram-se estáveis ao longo dos 60 dias em relação aos parâmetros físicos e oxidação lipídica. Os produtos com substituição de nitrito de sódio mostraram um tendência de aumento de intensidade de coloração amarela mais acentuada do que os produtos com adição de cloreto de sódio. A análise sensorial demonstrou que não houve efeito significativo da redução do NaCl sobre atributos gosto salgado e sabor. Em relação à estabilidade microbiológica, todas as formulações apresentaram resultados similares e considerados aceitáveis em relação às normas de legislação. A condução desse trabalho permitiu a elaboração de um embutido cozido de peru com redução de sódio e substituição de nitrito de sódio por uma fonte natural de nitrato com resultados que garantem a viabilidade tecnológica dessa reformulação promovendo apelos mais saudáveis para essa categoria de produto cárneo / Abstract: During developing meat products with healthy appeal, sodium reduction and replacement of sodium nitrite are important strategies to be implemented by the processing industry. Products with reduced sodium can be found in markets stores, although, the production of these goods with sensory acceptance and technological performance is still a great challenge. This study aims to evaluate the effect of reducing sodium chloride and the replacing sodium nitrite by celery extract in cooked turkey breast. Potassium chloride and a bitter taste masking were selected as a sodium chloride replacer, and celery extract and starter culture as substitute of sodium nitrite and reduction agent respectively. The replacement levels of sodium chloride by potassium chloride were evaluated at: 25%, 50% and 75%. At first stage of the study sodium reduction was evaluated with a focus on sensory attributes. According to sensory evaluation, it was concluded that the reduction of 25% NaCl can be accomplished without affecting product acceptance. In the second step, manufacturing process was asset for application of the extract of celery and starter culture as substitutes for sodium nitrite. Finally, the third phase were prepared formulations with replacement of NaCl by KCl and bitter mask taste (25%, 50% and 75% replacement) with the addition of sodium nitrite and sodium nitrite substitution for celery extract, as a source of nitrate and starter culture, such as source reduction. The stability of formulations were evaluated over 60 days of storage at 4 ° C, through physical-chemical determinations, instrumental, sensory and microbiological. Through the analytic determinations showed that all formulations were stable over the 60 days. The instrumental analysis (determination of color throughout the period of shelf-life of sliced and products exposed to light) showed a trend of replacing products with sodium nitrite present intensity of yellowish sharper than the products with added sodium chloride, and the sensory analysis showed that the effect of reduction of NaCl did not alter this sensory attribute. Regarding microbiological stability, all formulations showed similar results and considered acceptable. The conduct of this work allowed the preparation of a built-cooked turkey with sodium reduction and replacement of sodium nitrite by a natural source of nitrate with results that promote healthier appeals to this category of meat product / Mestrado / Mestre em Tecnologia de Alimentos

No description available.

Cette thèse a été réalisée initialement dans le cadre du projet Stockage Thermique Appliqué à l’extension de Production d’énergie Solaire thermodynamique (STARS) soutenu par l'Agence De l'Environnement et de la Maîtrise de l'Energie (ADEME).L’objectif du projet est de développer une solution de stockage thermique adaptée à la technologie Fresnel à génération directe de vapeur avec une zone de stockage de chaleur latente. Dans une unité de stockage latent, le nitrate de sodium (NaNO3) a été choisi comme matériau à changement de phase (MCP) et l’acier faiblement allié a été envisagé comme matériau de structure du conteneur et de l’échangeur thermique. La contribution de la thèse se positionne au niveau de l’étude de la corrosion et de la durabilité des matériaux de structure (conteneur et échangeur) en contact avec le MCP. L’objectif est de déterminer une loi de vitesse de corrosion qui permettrait de dimensionner les parois de l’échangeur et de développer des protocoles utilisant les techniques électrochimiques afin de suivre in-situ l’état de la corrosion au sein de l’unité de stockage. Les travaux présentés dans ce manuscrit portent sur l’étude expérimentale de la corrosion de l’acier dans le nitrate de sodium fondu à 340°C en fonction des paramètres expérimentaux tels que la présence d’impuretés (oxydes, chlorures), l’atmosphère gazeuse et le cyclage thermique. L’étude par mesures gravimétriques met en évidence la formation d’une couche de corrosion protectrice en surface de l’acier et la production de nitrite de sodium (NaNO2) par la réaction de corrosion. Cette couche constituée principalement de Fe2O3 (insoluble dans NaNO3 fondu) a été caractérisée par différentes méthodes d’analyse de surface (DRX, XPS). L’évolution de l’épaisseur de la couche de corrosion obtenue par cette technique montre une cinétique de corrosion logarithmique dans NaNO3 pur et une cinétique linéaire en présence d’une teneur importante en impuretés chlorures (10 mol%). L’étude électrochimique a apporté des indications sur le comportement du fer (et de l’acier) dans NaNO3 fondu. En combinant ces données avec les observations expérimentales issues des essais de corrosion nous avons pu proposer un mécanisme réactionnel pour la corrosion de l’acier en milieu nitrate fondu. L’étude par spectroscopie d’impédance électrochimique a permis de valider le mécanisme réactionnel proposé. A l’aide de ce mécanisme, les paramètres cinétiques puis la valeur du courant de corrosion ont été déduits par simulation des diagrammes d’impédance. L’analyse de la variation du courant de corrosion en fonction du temps permet de calculer l’épaisseur de la couche de corrosion et de la comparer à celle obtenue par gravimétrie. Un bon accord entre les valeurs obtenues par différentes techniques a été observé.Au cours de ce travail, nous avons également montré la possibilité d’utiliser les techniques électrochimiques pour l’instrumentalisation des installations industrielles afin de suivre in-situ l’évolution de la composition du MCP et l’état d’avancement de la corrosion de l’acier.Enfin, ce travail a montré que l’acier faiblement allié est adapté pour être utilisé dans une unité de stockage latent avec le nitrate de sodium comme matériau à changement de phase. / This thesis was originally performed as part of the STARS project (Stockage Thermique Appliqué à l’extension de Production d’énergie Solaire thermodynamique) which was supported by ADEME (l'Agence De l'Environnement et de la Maîtrise de l'Energie). The objective is to develop a thermal storage system using latent heat from a phase change material (PCM) in order to match with Fresnel technology using direct steam generation. Sodium nitrate (NaNO3) has been selected as PCM and low-alloy steel has been considered as candidate material to build the container and the heat exchanger of a latent heat storage system. The contribution of this thesis is to provide better understanding of the corrosion of the candidate material in contact with the PCM. This thesis aims to determine a corrosion rate law which helps design the thickness of the heat exchanger’s wall and to develop protocols using electrochemical technics to follow in-situ corrosion process in the latent heat storage system. The work presented in this manuscript focuses on experimental study of corrosion of low-alloy steel in molten NaNO3 (340°C) in function of different parameters: presence of impurities (oxides, chlorides), atmosphere and thermal cycling. Gravimetric measurements reveal the formation of a protective corrosion layer on the steel’s surface and the production of sodium nitrite (NaNO2) by corrosion reaction. The corrosion layer consisting mainly of Fe2O3 (insoluble in molten NaNO3) was characterized by surface analytical methods (XRD, XPS). Variation of the thickness of corrosion layer obtained by gravimetric methods shows logarithmic kinetics in pure NaNO3 and linear kinetics in the presence of 10mol% of impurity chlorides. Electrochemical study has provided indications on the iron (and steel) behavior in molten NaNO3. By combining results of this study with experimental observations from gravimetric study, we were able to propose a corrosion mechanism of the steel in molten NaNO3. This mechanism was then validated by electrochemical impedance spectroscopy study. Kinetics parameters and value of corrosion current were deduced by the simulation of impedance diagrams using the proposed mechanism. The thickness of corrosion layer was calculated by analyzing the variation of the corrosion current with time. These values present a good agreement with values obtained by gravimetric study.In this work, we also show the possibility of using electrochemical measurements at industrial scale to follow in-situ the evolution of the PCM's composition and the corrosion state. Finally, this work has shown that low-alloy steel is suitable for using in a latent heat storage system with NaNO3 as phase change material.

Le travail présenté dans ce manuscrit concerne le développement d’un système de stockage thermique par chaleur latente pour les centrales solaires à concentration utilisant la génération directe de vapeur, et s’attache plus particulièrement la sélection et l’étude du matériau à changement de phase (MCP). Cette thèse a été réalisée dans le cadre du projet Stockage Thermique Appliqué à l’extension de pRoduction d’énergie Solaire thermodynamique (STARS) porté par le consortium composé d’AREVA Renouvelables, la société Hamon d’Hondt, l’institut CEA liten et les laboratoires IPNO, LPCS et LaTEP. Ce projet est accompagné par l’ADEME dans le cadre du programme énergies décarbonnées des investissements d’avenir.Le premier chapitre de ce manuscrit situe le contexte de l’étude en dressant un état de l’art des différents systèmes solaires à concentration existants et des différents moyens de stocker l’énergie pour ce type de technologie. Le projet STARS est ensuite présenté. Ce chapitre se termine par un descriptif des objectifs du travail de thèse. L’intégralité du processus de sélection du MCP, incluant le recensement des matériaux dans la littérature, la définition des critères de sélection et la caractérisation par calorimétrie différentielle à balayage des candidats les plus pertinents, est détaillée dans le chapitre II. À l’issue de ce travail, le choix du consortium se porte sur le nitrate de sodium, un sel inorganique possédant une température de fusion adaptée à la technologie d’AREVA et une densité de stockage importante. La poursuite de l’étude, concernant la stabilité thermique du MCP durant son utilisation en conditions industrielles, fait l’objet du chapitre III. Cette étude comporte une partie bibliographique permettant de mettre en évidence les problématiques liées à la dégradation thermique du matériau et à son comportement vis-à-vis des matériaux métalliques avec lesquels il sera amené à être en contact (échangeur de chaleur, cuve de stockage). La principale conséquence des phénomènes mis en évidence étant la réduction du nitrate de sodium en nitrite de sodium, l’étude de l’impact du taux de nitrite de sodium sur les propriétés thermiques du MCP a été réalisée. Les résultats de cette campagne expérimentale ont montré une diminution significative de la température de fusion et de la chaleur latente du MCP lorsque la proportion de nitrite de sodium croît. Afin d’étudier l’évolution de composition du MCP dans des conditions réelles de fonctionnement, un dispositif a été conçu spécifiquement pour reproduire des conditions de cyclage thermique en présence de métaux. L’étude menée à l’aide de ce dispositif a permis d’analyser la cinétique de réduction du nitrate de sodium en nitrite de sodium. Les résultats montrent que l’évolution de composition du MCP dans les conditions opératoires du projet est négligeable, garantissant la stabilité des propriétés thermiques de celui-ci au cours de son utilisation.Enfin, le dernier chapitre est consacré à l’étude de l’amélioration des transferts thermiques au sein du MCP. En effet, le nitrate de sodium possède une conductivité thermique faible, pouvant limiter la puissance des échanges de chaleur dans le système de stockage. En premier lieu, un état de l’art des solutions d’intensification des transferts dans le domaine du stockage par chaleur latente est dressé. Ce travail a permis de mettre en évidence que l’utilisation de composites à base de mousses métalliques constitue une voie pertinente d’amélioration des transferts. Ainsi une campagne expérimentale visant à évaluer les performances de tels composites a permis de mettre en évidence le potentiel de ce type de configuration. / The work presented in this manuscript concerns the development of a latent heat thermal energy storage system adapted to concentrated solar power plant using direct steam generation, and more particularly on the selection and the study of the Phase Change Material (PCM) used in this system. This thesis was performed within the framework of the STARS project (Stockage Thermique Appliqué à l’extension de pRoduction d’énergie Solaire thermodynamique) carried by the consortium of AREVA Renouvelables, Hamon d’Hondt company, CEA institute liten and laboratories IPNO, LPCS and LaTEP. This project is accompanied by ADEME under the énergies décarbonnées des investissements d’avenir program. The first chapter of this manuscript sets up the context of this study by drawing a state of art of different existing CSP technologies and various ways to store energy for this kind of systems. The STARS project is then described. This chapter ends with a description of the thesis objectives. The entire PCM selection process, including identification of materials in literature, definition of various criteria and thermal characterization by differential scanning calorimetry (DSC) of the most relevant candidates, is detailed in chapter II. This work leads to the selection of sodium nitrate by the consortium, an inorganic salt with a suitable melting temperature considering AREVA’s technology and a large storage density. The following work, concerning the thermal stability of the PCM under thermal cycling, is then presented in chapter III. This part includes a bibliographic study allowing to highlight issues related to thermal degradation of the PCM and its behavior regarding to metallic material with which it will have to be in contact (heat exchanger, storage tank). The main consequence of these phenomena is the reduction of sodium nitrate into sodium nitrite, and thus the impact of sodium nitrite fraction on the thermal properties of the PCM was studied. The results of this experimental work shows a significant reduction of the melting temperature and the latent heat as the fraction in sodium nitrite increases. To study the evolution of the PCM composition under real operating situation, a specific device was designed to replicate thermal cycling conditions in the presence of metals. This device was used to analyze the kinetics of reducing sodium nitrate into sodium nitrite. The results show that the changes in composition of the PCM in the project’s operating conditions are negligible, ensuring the stability of its thermal properties during its lifetime. The last chapter is devoted to the improvement of heat transfers within the PCM. Indeed, sodium nitrate has a low thermal conductivity which may limit the power of the heat exchange in the storage system. A state of art of available solutions for the intensification of thermal transfers concerning latent heat storage was done. This study highlighted that the use of composites based on metallic foams constitutes an effective way of improvement. Thus an experimental campaign was conducted to evaluate the performances of such composites, allowing to show the potential of this kind of configuration.